BP - Circadian rhythms Flashcards
what is an endogenous pacemaker
the body’s internal clock that regulates biological rhythms e.g. SCN
what are exogenous zeitgebers
external factors in the environment which reset our biological clock
what is the SCN
- suprachiasmatic nucleus
- found above the optic chiasm that is connected to the pineal gland
- known as the master clock
evidence of the SCN (endogenous pacemaker)
- hamsters with the Tau mutation have a circadian rhythm of 20h compared to 24h of normal hamsters
- when the SCNs were swapped, their circadian rhythm lengths swapped
- evidence of the main endogenous pacemaker
what does the pineal gland produce
melatonin
what is the function of melatonin
induces sleep and is inhibited when one is awake (causal factor in SAD)
what does zeitgeber mean
time-giver
how is light an example of an exogenous zeitgeber
- can reset the SCN
- plays a key role in the maintenance of the sleep-wake cycle
- has an indirect influence on hormone secretion
- study suggests that light can be detected by skin and eyes
how are social cues an example of an exogenous zeitgeber
- circadian rhythms start at 16 weeks -> mostly influenced by parents
- research suggests that adapting to local eating and sleeping times is the best way to beat a circadian rhythms
what does the Michel Siffre cave study display
- 1962, a cave explorer spent 2 months living in total isolation without access to a clock
- he slept and ate when his body told him to
- he settled into a sleep-wake cycle of 25-30h - became desynchronised
evaluation of Michel Siffre cave study
- demand characteristics
- not generalisable as it was only done on him
AO3: practical application to shift work
P: shift work has been found to lead to desynchronisation of circadian rhythms
E: research shown that night shift workers suffer a concentration lapse at 6am, increasing likelihood of accidents
E/L: this suggests that the body’s external clock is set to 24’25h
AO3: poor control in studies
P: in the cave studies there was exposure to artificial light like torches
E: it was assumed it was only natural light that has an influence on biological rhythms but it could be artificial
E: the results of the original study may lack validity and the sleep wake cycle may vary more
